Article

Can artificially selected phenotypes influence a component of field fitness? Thermal selection and fly performance under thermal extremes

Center for Environmental Stress and Adaptation Research, Department of Genetics, The University of Melbourne, Victoria, Australia.
Proceedings of the Royal Society B: Biological Sciences (Impact Factor: 5.29). 04/2007; 274(1611):771-8. DOI: 10.1098/rspb.2006.0247
Source: PubMed

ABSTRACT Artificially selected lines are widely used to investigate the genetic basis of quantitative traits and make inferences about evolutionary trajectories. Yet, the relevance of selected traits to field fitness is rarely tested. Here, we assess the relevance of thermal stress resistance artificially selected in the laboratory to one component of field fitness by investigating the likelihood of adult Drosophila melanogaster reaching food bait under different temperatures. Lines resistant to heat reached the bait more often than controls under hot and cold conditions, but less often at intermediate temperatures, suggesting a fitness cost of increased heat resistance but not at temperature extremes. Cold-resistant lines were more common at baits than controls under cold as well as hot field conditions, and there was no cost at intermediate temperatures. One of the replicate heat-resistant lines was caught less often than the others under hot conditions. Direct and correlated patterns of responses in laboratory tests did not fully predict the low performance of the heat selected lines at intermediate temperatures, nor the high performance of the cold selected lines under hot conditions. Therefore, lines selected artificially not only behaved partly as expected based on laboratory assays but also evolved patterns only evident in the field releases.

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    • "However, unlike the phenotyping assays where files were stressed at 38.5 °C until complete knockdown (from which some flies do not recover), the flies for the transcript assays were subjected to a partial knockdown to ensure that stress-induced transcript expression was not confounded with apoptosis. Further, we deemed it more ecologically relevant to profile flies under extreme stress from which they can recover and survive to reproduce, given that static measures of heat knockdown have been linked to fitness in response to extreme temperature under field conditions (Kristensen et al. 2007). To this end, the time-course was determined by assessing mortality rates 48 h after exposure to increasing increments of heat stress (i.e. 5, 10, 15 min and onwards exposure to heat stress). "
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